The Blues that the novel refers to is not just a sad mood or something. Actually, the tragedy that Jacques discovers in this book goes beyond the scope of the book. Jacques finally finds his brother, whom he was partially responsible for in the past, he feels now, and whom he feels he disappointed. But when he finds the brother, named Theo, interestingly, he discovers that the forgiveness he seeks is complete irrelevant now—his brother has been incapacitated by fate, and he can no longer recognize his loved ones, because of his chronic amnesia.
In other words, Jacques discovered the meaning of human life, but in two strikingly opposite ways. Since he wants this journey to be useful in the creation of his next novel (a witty meta-cognitive move by the author), we should look at the whole of his adventure to get a full picture of his argument. In his opinion, the meaning of life is to share an adventure with a kind, attractive stranger who you get to know in your pursuit for an answer to a question that is difficult to even phrase.
So if Theo's horrific state is the answer to their existential questioning, then where is the meaning? Is it in the tragedy? Is their time together now a waste of time, because they found something they weren't expecting? By the way, what is it that Jacques even finds in that moment, that he should be so confident that he has discovered his next novel? It is simply this: upon realizing the truth about Theo's condition, Jacques feels a tremendous agony, a pain so explicit and severe that he permanently learns a meaningful lesson—nothing on earth is more important than doing what we can for our loved ones.
